The invention relates to the manufacture of semiconductor circuits on semiconductor wafers, and more particularly to chemical vapor depositions of materials on the wafer.
A large number of nonvolatile metal organic precursors which are suitable in microelectronics applications for chemical vapor deposition (CVD) of thin films are solids at temperatures at or below 1500 Kelvin and at pressures at or above 10xe2x88x9210 Torr. In fact, a majority of metal-organic compounds with attributes desirable for CVD are solids. These compounds have chemical stability, molecular structures, and reactivity which make them ideally suited for CVD application. However, vapor transport is difficult to perform under temperatures and pressures typically utilized in semiconductor manufacture. Thus, vapor transport of these precursors is a major hinderance to the implementation of the precursors in a production environment. If the precursor has a sufficient vapor pressure, then sublimation of the precursor for transportation of its vapor is the only option available, however this is difficult to control in a manufacturing environment. Solid precursors have been dissolved, transported, and delivered in organic solution, but these solutions usually leave a large carbon residue.
It is an object of the invention to provide reliable production worthy methods for fast delivery of nonvolatile precursors to the chemical vapor deposition (CVD) chamber.
The invention features dissolving a nonvolatile precursor, either solid or liquid, in a solution and delivering the precursor in the solution to a CVD chamber.
The invention is a very efficient method for transporting a nonvolatile precursor for CVD in the manufacturing environment and incorporates a minimum amount of unwanted by-product in the desired film. The method entails a process which is easily controlled and therefore predictable with repeatable results.
The invention includes apparatus adapted to carry out a method directed to the use of a nonvolatile precursor, either solid or liquid, in a chemical vapor deposition (CVD) process. A solid precursor, as referenced herein, is a precursor which is in a solid state at a temperature at or below 1500 Kelvin and at a pressure at or above 10xe2x88x9210 Torr, and a liquid precursor, as referenced herein, is a precursor which is in a liquid state at a temperature at or below 1500 Kelvin and at a pressure at or above 10xe2x88x9210 Torr. Using the method of the invention the nonvolatile precursor is dissolved in a solvent to form a solution. The nonvolatile precursor is then transported in the solution at a pressure and a temperature necessary to maintain it as a liquid to the CVD chamber. The solution is transported in a continuous liquid stream to the CVD chamber. A continuous liquid stream is an unbroken non-nebulized stream of liquid which may be passed to the chamber without interruption or may be passed to the chamber in a pulse or batch. The pulse or batch can be thought of as a portion of the solution.
In a first embodiment the solution becomes a gas during rapid evaporation of the solution at a high temperature and at a low pressure. The gaseous form of the precursor reacts with a reactant at the heated surface of the wafer.
In a second embodiment the method of the invention can be used in liquid source chemical vapor deposition where the solution is applied to the wafer before being evaporated.